The process of lithography involves the transfer of a pattern to photosensitive material using light or another suitable radiation source. That is, when photosensitive material is exposed to radiation while regions of the material are masked, the radiation pattern is transferred to the exposed or unmasked material due to the difference in the properties of the exposed and unexposed regions. In this manner various lithographic products may be produced. Certain laser lithography or photolithography processes use a laser beam having a narrow beam width as the radiation in order to imprint precise patterns onto a substrate.
Focusing a laser beam using conventional optical lenses may be limited by the achievable beam-waist of a Gaussian photon profile. That is, one must decrease the focal distance of a conventional optical lens in order to achieve a finely-focused diameter. Focusing light into a beam having a diameter less than the wavelength of the photons may be extraordinarily difficult to achieve. Phase-contrast (PC) lithography processes that use PC masking techniques may enhance the available optical resolution. However, PC masking is known to be relatively expensive, with a different PC mask typically being fabricated for each required lithography pattern.